The art associated with the present invention is the art of apparatus which produce motion. Various apparatus may be found in numerous different contexts, which impart motion in some form. For purposes of providing at least one context in which such an apparatus may be useful, much of the following is devoted to the context of continuous, passive motion apparatus. The present inventor has recognized several uses for the apparatus of the present invention in addition to use with or as a continuous, passive motion machine. Human joints, and muscles associated with the joints, may be weakened or traumatized as a result of disease, injury or a surgical procedure. Prolonged inactivity of the joint can be a deterrent to recovery and can result in reduced limits of joint function. Movement of the joint hastens and improves rehabilitation, but may be difficult or painful for a patient. Consequently, the art has recognized the need for machines which can provide passive exercise, operating the joints and flexing the muscles over restricted limits which may be increased as rehabilitation progresses.
A variety of such apparatus has been proposed and are commonly called continuous, passive motion or CPM systems. With a CPM system it is desirable to drive a foot supporting platform not only in dorsiflexion and plantar flexion over a range of angular displacement, but also in eversion and inversion over a range of angular displacement. Preferably, a CPM machine can provide both simultaneously and in a smoothly blended, continuous motion.
Apparatus proposed by the art suffers from one or both of two principal disadvantages. Several such devices generate only one motion. Others either do not permit adjustments in the angular displacement range over which the foot support platform is driven or, at best, have adjustments which are difficult for the therapist to make and/or can be varied only over a relatively narrow range. Most require an inconvenient mechanical adjustment of the apparatus.
It is one object and feature of the present invention to provide a therapeutic CPM machine which imposes a continuous, passive motion upon a support platform for supporting a foot or other extremity, such as a hand, with the motion being easily controlled and varied without mechanical adjustment over a broad range of inversion and eversion angular displacement and speed, and simultaneously over a broad range of dorsal and plantar flexion angular displacement and speed. This allows a therapist to select and change, from time to time, the amplitude and speed of the angular excursions and the angle of the limits of those excursions in both the eversion/inversion direction, as well as in the dorsal/plantar flexion direction.